A brief congressional hearing ended in shouting and confusion on Wednesday after a former US Internal Revenue Service official refused to answer questions about a 10-month-old controversy involving IRS scrutiny of conservative political groups. Lois Lerner, who was at the center of last year's so-called Tea Party targeting scandal, declined to answer questions from Darrell Issa, the Republican chairman of the House of Representatives Oversight and Government Reform Committee

Washington — A House Oversight Committee hearing on whether the Internal Revenue Service unfairly targeted conservative political groups for scrutiny degenerated into near-chaos Wednesday as a key witness refused to testify and the Republican panel chairman cut off the microphone of the ranking Democrat as he attempted to speak.

Shouting ensued, some of it electronically amplified, some not. Eventually committee chairman Rep. Darrell Issa (R) of California left the room and held a press conference just outside, drawing the crowd with him.

“Mr. Chairman, what are you hiding?” said the visibly agitated Rep. Elijah Cummings (D) of Maryland as Rep. Issa walked away.

Long story short, the IRS investigation is a highly fraught subject. And Wednesday’s hearing frustrated both sides for different reasons.

It began with former IRS official Lois Lerner invoking the Fifth Amendment against self-incrimination and refusing to answer committee questions. Ms. Lerner is the former head of the unit of the IRS that investigated applications for tax exempt status for political groups, and thus a key figure in the investigation.

She took the Fifth at a May hearing as well, but she also delivered a statement defending herself before refusing to answer questions. GOP committee members think it’s an open question as to whether this statement constituted a waiver of her Fifth Amendment rights, and there was some talk in congressional halls that she’d testify at Wednesday's hearing. But she didn’t, and now the Republican House leadership may up the pressure.

Speaker John Boehner said Wednesday he would wait for a report on the issue but that “she has to testify or she should be held in contempt” of Congress. That could lead to a court ordering her to speak.

Republican members of the committee were particularly frustrated because they think they’ve got some documentary evidence that establishes a motive for Lerner’s office to unfairly target conservative groups applying for tax exempt status under section 501 (c) 4 of the tax code.

Investigators have obtained IRS e-mails that show Lerner was very concerned about the impact of the Supreme Court’s Citizens United ruling on political spending, according to a report in Politico.

Republicans think Lerner may have wanted to limit the political activity of conservative groups to level the political field. Lerner’s lawyer has called that assertion “fiction,” and the text of the e-mails made public so far don’t seem to indicate any party bias on Lerner’s part.

“My object is not to look for political activity – more to see whether self-declared c4s are really acting like c4s,” she wrote at one point, according to the Politico story.

Without Lerner’s testimony that may be as far as the trail leads, said Issa after the contentious hearing.

“At this point, roads lead to Ms. Lerner,” he said. “It may dead-end at Ms. Lerner” if she does not talk at some point.

This apparent dead end has led some conservatives to wonder why the committee does not just do what Lerner’s lawyer wants, and give his client immunity from prosecution in return for her testimony.

“Maybe Issa and the GOP are worried that conservatives will be angry with them if they let Lerner walk. That’s a small price to pay, though, if she has incriminating info on others up the chain,” writes right-leaning Allahpundit at the Hot Air site.

Democrats, for their part, say Issa has spent years on open-ended investigations of alleged Obama administration wrongdoing and has little to show for it. They’re frustrated by what they say is the autocratic way he conducts committee business. That’s what finally appeared to put Representative Cummings, a liberal whose district includes half of Baltimore, over the edge.

It started just after Lerner declined to speak. Issa, who appeared frustrated, tried to adjourn the hearing. He stood up as if to depart.

Cummings said he had a procedural question. “Mr. Chairman, you cannot run a committee like this. You cannot do this. We’re better than that as a country. We’re better than that as a committee.

At that point Issa leaned over and switched off Cummings’ mike.

“If you will sit down and allow me to [ask] the question, I am a member of the Congress of the United States of America, I am tired of this,” an unplugged Cummings bellowed into the room.

Afterward, Cummings said that as far as he is concerned, Lerner has not waived her Fifth Amendment rights. Nor has the investigation shown any political motivation by IRS agents, or any links to anyone in higher office, including the White House, said the Democratic lawmaker.